Process and an apparatus for the production of synthetic, crimped, highly elastic endless yarn

ABSTRACT

A process for the production of a crimped yarn of synthetic, thermoplastic filaments or bundles of filaments by false twisting two filaments or two bundles of filaments 5,000-15,000 twists per meter after the filaments have been heated sufficiently to fix the twist and plied together before being subjected to the false twister.

United States Patent Heinroth et a1.

[ June 18, 1974 Bayer Aktiengesellschaft, Leverkusen, Germany Filed: May7, 1973 Appl. No.: 357,610

Related U.S. Application Data Assignee:

1971, abandoned.

[56] References Cited UNITED STATES PATENTS Continuation-in-part of Ser.No. 112,118, Feb. 3,

U.S. Cl. 57/34 HS, 57/157 TS Int. Cl. D0lh 13/26, 002g 1/02 Field ofSearch... 57/34 R, 34 HS, 77.3-77.45,

57/140 R, 140 B, 157 R, 157 TS, 157 MS Hilleary et a1. 57/34 HS XFOREIGN PATENTS OR APPLICATIONS Primary Examiner-Donald E. WatkinsAttorney, Agent, or Firm-Plumley & Tyner ABSTRACT twister.

2 Claims, 2 Drawing Figures PROCESS AND AN APPARATUS FOR THE PRODUCTIONOF SYNTHETIC, CRIMPED, I-HGTHJY ELASTIC ENDLESS YARN This is acontinuation-in-part of our pending patent application, Ser. No.112,118, now abandoned filed by us on Feb.3, 1971.

This invention relates to a process for the production of synthetic,crimped, highly elastic, endless yarns with a reduced tendency towardstwisting by the false-twist technique, and to an apparatus for carryingout the process.

It is known that filaments of synthetic material can be crimped by thefalse-twist method. To this end, the filament to be treated is heavilytwisted, fixed in this twisted form and then continuously untwisted. Thefilament thus produced shows a tendency towards twisting correspondingto the direction produced by the false twister during texturing. Inorder to prevent the stitch pattern of knitted fabrics from becomingdistorted due to the tendency which the yarn has towards twisting, twofilaments which show a tendency towards twisting in mutually oppositedirections are normally processed in a form in which they are twistedtogether.

It is also known that this tendency towards twisting can be reduced byan oppositely directed, false-twist process following the originalfalse-twist process. Unfortunately, the second crimping treatment takesplace on account of a reduction in the crimp effect.

These known processes and apparatus are generally highly involved fromthe point of view of practical application and in some cases only permitlow rates of travel. Above all, it must be pointed out that conventionalprocesses can only be used for very narrow denier ranges. Particularreference is made in this connection to the average-denier range forwhich nobody has yet developed a process that works satisfactorily fromthe economical point of view; namely, the range from 100 to 400 dtex.

It is an object of this invention to provide a process for theproduction of synthetic thermoplastic endless yarns with a particularlybulky, highly voluminous and highly elastic character.

This object is achieved by a process for the production of a crirnpedyarn consisting of synthetic, thermoplastic filaments or bundles offilament which comprises false-twisting in the same direction a ply oftwo filaments or of two bundles of filaments in the amount of about5,000 to 15,000 twists per meter immediately after each filament orbundle in the ply has been separately heated sufficiently to fix thetwist in the filaments or bundles and plied by bringing the twofilaments or the two bundles to the point of plying at an angle betweenfilaments or bundles of approximately 60.

By virtue of the process according to the invention, it is possible toproduce in a single twisting and heating operation a highly elastic yarnwith a reduced tendency towards twisting. This is accomplished byproviding two synthetic filaments or two bundles of filaments which arefalse-twisted at a high rate of speed shortly after the filaments orbundles have passed through the heated fixing zone. The high rate ofspeed causes the filaments or bundles periodically to lose contact withthe twister and to unroll in the opposite direction from that impartedby the twister. This produces alternating segments of the filament orthe bundle in which the twist has changed direction, e. g. from S- to Z-direction or from Z- to 8- direction. Both twists are fixed in a singleoperation by the heat supplied to the filaments or bundles by theheater.

The process according to the invention is eminently suitable fortexturing filaments or bundles of filaments of fully synthetic highpolymers, especially polyamides and high molecular weight linearpolyesters and acrylonitrile polymers.

It is another object of the invention to provide an apparatus forcarrying out the process. This object is accomplished by a crimpingapparatus comprising a pair of filament separating units; means fordelivering filament or filament bundles to the separating units; aheating unit which heats the filament or filament bundles separately; adoubling unit; and a false twister; the arrangement being such thatafter the false twist is imparted to the filaments or bundles veryquickly after they leave the heating unit, and the heat is sufficient tofix the twist in the filaments or bundles in whatever direction itexists.

The apparatus and process of this invention are illustrated in theattached drawings. FIGS. 1 and 2 are identical, except that the finaltwisted ply of filaments is wound on a single cop in FIG. 1 and isseparated and wound on two cops in FIG. 2. According to FIG. 1, thefilaments 1 and 2 coming from the bobbins are plied together and travelthrough the delivery mechanism 3 to the two separating units 4 and thenover the heating unit 5, the two separating units 6 to the false twister7. The filaments then travel through the take-ofi' mechanism 8 to thewinding mechanism 9. Due to the twist imparted by the false twister 7, afalse twist is produced in the section A/B between false twister 7 andseparating units 6. Due to the fact that the filaments or bundles offilaments momentarily lose contact with the twister and momentarilyunroll in the opposite direction, the individual filament or bundle offilaments contains alternate portions or segments with opposite twists.The heating unit 5 fixes whatever twist is in the individual filamentsor bundles of filaments and in the double filament because the distancebetween the heating unit and the separating units is so short that thefilament is still hot enough to fix the twist as it travels into thedoubling unit 10 to form a ply of two filaments or bundles of filaments.

The angle for optimum setting at the doubling point amounts toapproximately 60. At angles smaller than this, the crimp effect assumesa fine-arc configuration, whilst at larger angles it assumes a large-arcconfiguration. The false-twist crimping is carried out at elevatedtemperatures (fixing) in the range from to 220 C. The number of twistsamounts to between 5,000 and 15,000 per meter.

FIG. 2 shows that the filaments treated as described above can beseparated in the component section C/D and separately wound-up.

The following examples further illustrate the invention without limitingit.

EXAMPLE 1 Two already stretched polyamide-6 filaments of dtex 44 f 9 areunwound from the take-off godet 3 (cf. FIG. 1) at a rate of 392 metersper minute and travel through guides 4 and 6, the heating unit 5, theinternal friction twister 7 to the take-off godet 8 which is set to workat 400 meters per minute, equal to a 2 percent difference in speed inrelation to the take-off godet 3.

The filaments are then wound together on cops 9. The direction of thetwist imparted by the false-twister 7 is the S-direction in thecomponent section A/B (of. FIG. 1.) and in the Z-direction in thesection C/D. By virtue of the fact that the filaments are fixed in theirposition by the guides 6, the false twist can only run in the S-direction to guides 6.

The heating unit 5 has a temperature of 180 C. The peripheral speed ofthe twister is adjusted in such a way that the filament undergoesapproximately 8,000 falsetwists per meter in the S-direction. The yarnthus produced shows alternate segments of S-twist and Z-twist and acrimp contraction of approximately 50 percent for a shrinkage in steamaccording to Wegner of 11 percent (cf. Mell. 5, 1966, pages 493-495).The yarn has a final denier of 88/18 dtex.

EXAMPLE 2 Two unstretched polyamide-6 filaments of dtex 100 f 24 aretreated as in Example 1, except that the speed of the godet 3 amounts to108 meters per minute and the speed of the godet 8 to 400 meters perminute, giving a stretching ratio of 1:3.7. The temperature of theheating unit 5 is 190 C. The yarn thus obtained has a crimp contractionof approximately 45 percent for a shrinkage in steam of approximately 14percent. The final denier amounts to 200 f 48 dtex.

EXAMPLE 3 The conditions are as described in Example 2, except that thebundles of filaments undergoing the texturing treatment are separatedbehind the false twister 7 in the component section C/D, unwound fromthe two godets 8 and wound on two cops 9. The final denier amounts to100/24 dtex. The yarn thus obtained has a crimp contraction of from 40to 45 percent for a shrinkage in steam of approximately 16 percent.

EXAMPLE 4 Two unstretched polyamide-6,6-filaments of dtex 22 f 3 aretreated as described in Example 2 except that the speed of godet 3amounts to meters per minute whilst the speed of godet 8 amounts to 500meters per minute, giving a stretching ratio of 113.22. The temperatureof the heating unit amounts to C. As in Example 3, the bundle offilaments are separated behind the false-twister 7 in the componentsection C/D, unwound from the two godets 8 and wound on two cops 9. Thefinal denier amounts to 22 f 3. The yam thus obtained has a crimpcontraction of from 50 to 55 percent for a shrinkage in steam of 9percent.

What is claimed is:

1. A process for the production of crimped yarn of syntheticthermoplastic filaments or bundles of filaments which comprisessimultaneously false twisting in the same direction a ply of twofilaments or of two bundles of filaments in the amount of about 5,000 to15,000 twists per meter immediately after each filament or bundle in theply has been separately heated sufficiently to fix the twist in thefilaments or bundles and plied by bringing the two filaments or the twobundles to the point of plying at an angle between filaments or bundlesof approximately 60.

2. A crimping apparatus comprising a false twister capable of falsetwisting a ply of two filaments or two bundles of filaments of syntheticthermoplastic material, a heating unit capable of separately andsimultaneously heating two parallel traveling filaments or bundles offilaments, means for feeding two separate filaments or two separatebundles of filaments to said heating unit, means for plying together thetwo separate filaments or the two separate bundles of filaments leavingsaid heating unit and immediately passing the ply to said false twister,means for stretching said ply between points ahead of said heating unitand after the exit of I said false twister, means for applying to saidply 5,000 to 15,000 twists per meter by said false twister, and meansfor winding up the heat fixed ply exiting said false twister.

2. A crimping apparatus comprising a false twister capable of falsetwisting a ply of two filaments or two bundles of filaments of syntheticthermoplastic material, a heating unit capable of separately andsimultaneously heating two parallel traveling filaments or bundles offilaments, means for feeding two separate filaments or two separatebundles of filaments to said heating unit, means for plying together thetwo separate filaments or the two separate bundles of filaments leavingsaId heating unit and immediately passing the ply to said false twister,means for stretching said ply between points ahead of said heating unitand after the exit of said false twister, means for applying to said ply5,000 to 15,000 twists per meter by said false twister, and means forwinding up the heat fixed ply exiting said false twister.